Base stations for generating microwave signals are known in the field of mobile telephony. Such base stations are connected to an antenna for transmitting the signals generated by the base stations to mobile telephones.
Often a plurality of base stations is connected to a single antenna. Each of the base stations may generate a microwave signal at a different frequency and different modulation scheme as is known in the art. In this case, each of the plurality of base stations is connected to an associated input port of a combiner. The combiner combines the signals from the input ports together and presents them at an output port, which is in turn connected to the antenna.
It is possible that the base stations may be incorrectly connected to the combiner or that transmit frequencies are incorrectly configured with respect to the respective pass-bands of the combiner. For example a base station adapted to generate a signal at one frequency may be accidentally connected to an input port of the combiner adapted to receive a signal at a different frequency. In such cases, and for certain types of combiners, such as directional-filter type combiners, the power from the incorrectly connected base station is delivered to an internal termination load in the combiner.
If some or all of the power from a base station is delivered to the internal termination load in the combiner then the apparatus will not operate correctly or possibly not at all. Permanent damage to the combiner, and especially to the internal termination load, may occur. Further, it can be difficult to determine the cause of such problems, and complex diagnostic systems may be required.